The present invention relates to inspection apparatus and inspection method for detecting foreign matters, flaws, contaminations and the like present on the surface of an object to be inspected such as a semiconductor wafer (hereinafter these defects will generally be described as foreign matters).
In an inspection apparatus for detecting foreign matters on a semiconductor wafer, an inspection optical beam such as a laser beam is irradiated on the surface of the wafer and reflection or scattering rays given off from the wafer surface are detected to detect a foreign matter present on the wafer surface.
In this type of inspection apparatus, when a pattern constituting chips is formed on the surface of the wafer, it is general practice that image signals are created from intensities of the detected reflection or scattering rays, an image signal of an inspection area (inspection chip or inspection shot) is compared with an image signal of a reference area (reference chip or reference shot) and a location where the difference between the two image signals exceeds a threshold value is determined as being indicative of a foreign matter (see JP-A-2002-250699). As the reference area, an area adjoining the inspection area (adjacent chip or adjacent shot) or an area of good quality prepared in advance (good quality chip or good quality shot) is used.
In inspecting the presence or absence of a foreign matter by comparing the inspection area with the reference area, an area having a perfect contour getting clear of a wafer edge (hereinafter referred to as a perfect area) is used as the reference area.